Types of Ultrasound

In 1957, a physicist by the name of William Nelson Beck was working on a scanner for fuel elements. By placing his arm in the area meant for the fuel element, “Nels” Beck discovered the ability to differentiate between bone and flesh, thereby inventing ultrasound.  Since that day, ultrasound technology has grown into one of the most widely used tools to diagnose and treat medical conditions. To the diagnostician, ultrasound technology provides real-time tomography images (images by section) of the body’s internal organs, structure and even blood flow.

Because ultrasound images are used in many areas, such as the abdomen, brain, heart, and organs, specific ultrasound tests have been developed. A popular diagnostic tool is the stress test. For those patients able to perform this test, they are instructed to wear loose and comfortable clothing as well as follow specific medication directions. Once connected to an EKG machine, the patient is instructed to walk on a treadmill or stationary bike. The exercise stimulates and increases the patient’s heart rate and blood pressure. The stress test shows the effects this exercise is having. For patients not able to exercise, medication is used to stimulate the same effects. Stress tests are used to diagnose coronary heart disease. Nuclear stress tests involve the injection of radioactive dyes. Images are then taken both at rest and after exercise, indicating areas of the heart receiving insufficient blood flow.

Some types of ultrasound require the insertion of the transducer into an orifice. Trans-vaginal ultrasounds are used to obtain images of a woman’s reproductive organs, the vagina, uterus, cervix and ovaries.This type of ultrasound is used when a patient complains of pelvic pain, if there is probability of an ectopic (tubal) pregnancy, a history of menstrual abnormalities or to determine to presence of cysts, fibroid tumors or growths.

Transrectal ultrasounds, obtained rectally, provide images for the organs in the pelvic (hip) area such as the prostate. Prostate cancer is the most common type of cancer for men in the United States. One in six men will be diagnosed with this form of cancer in their lifetime, making transrectal ultrasounds an important and life-saving diagnostic tool.

To obtain images of the heart, the most common type of ultrasound is a transthoracic echo. These images are obtained by using a transducer, about the size of a bar of soap, on the patients’ chest. Another form of heart image, a trans-esophageal echo cardiogram, is placed down the patient’s esophagus. Because the esophagus is mere millimeters from the heart, this test provides sharper and clearer images.

An innovative type of ultrasound is 3-D imaging, which allows the diagnostician to get a better picture of an organ, or fetus, rather than a two-dimensional ultrasound which presents a “slice’ of an image. In 3-D ultrasound imaging, the resulting image is captured by first taking multiple two-dimensional ultrasounds, either by surface or internal transducers. Once these images have been captured, they are then combined into 3-D images by specialized software. 3-D ultrasound imaging is of particular use in the detection of early cancerous growths, lesions or tumors. It is also used to obtain images of abnormal fetal development, as well as blood flow.

Doppler ultrasound was developed after the “Doppler effect”, the change in sound, wave frequency, as it approaches or leaves. This type of ultrasound bounces sound waves off of circulating red blood cells, allowing the ultrasound technician to measure blood flow and pressure through major arteries. For a patient having leg pain and numbness, their doctor may order a Doppler to be performed. The results will determine if the patient has adequate flow by detecting the blood’s pressure as it travels through the vessels. Doppler ultrasound is used to diagnose poor circulation from blood clots, defects such as malfunctioning vein valves, blockages in the arteries, aneurysms and stenosis (bulging or narrowing). Doppler ultrasound can allow the physician or surgeon to determine if a patient is a good candidate for procedures such as angioplasty. Other types of tests for blood flow and pressure such as arteriogram and venograms involve injecting dye into a patient’s blood vessels so they can be viewed. Doppler ultrasound provides these images with no painful injections or invasive procedures.

In obstetrics, there are several ultrasound tests used during the three trimesters of pregnancy such as standard and advanced ultrasounds, Doppler and 3 or 4-D ultrasounds. These tests are usually done in conjunction with blood tests and amniocentesis. Ultrasound can be used to confirm the heartbeat, measure the baby’s growth, search for abnormalities and verify the baby’s movements. Fetal Echocardiography provides images of an unborn child’s heart. The ultrasound technician will be able to capture images of the heart’s anatomy as well as function, allowing the physician to rule out congenital heart defects. Some pregnancies may not require ultrasound testing; however, if medically indicated or if there may be a risk for congenital defects, ultrasound is used.

Along with providing diagnostic images of the body’s organs, structure and vessels, ultrasound is used to guide physicians and surgeons during procedures such as a needle biopsy. Also known as a needle aspiration biopsy, this procedure allows the sampling of a small amount of cells from an abnormal area such as a mass. For a patient with a lump in her breast, a hollow needle is guided, by ultrasound, to the area of mass. Once withdrawn, the small cell group obtained is sent to the laboratory for testing. Often, needle biopsy supported by the guidance of ultrasound, can replace more invasive surgical procedures.

From images of an unborn child’s heart to blood flow and organs, the images produced by ultrasound have proved an invaluable diagnostic tool. Able to detect movement, function and even the intricacies of ligaments and tendons, ultrasound technology has become one of the most powerful and effective diagnostic tools today.

 

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